Initial commit

kapitel18/mygetip.c

@@ -0,0 +1,61 @@
+#define _XOPEN_SOURCE 700
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <netdb.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#define MAXSIZE 100
+
+int main(int argc, char *argv[])
+{
+   struct addrinfo hints, *res, *result;
+   char addrstr[MAXSIZE];
+   char host[MAXSIZE];
+   void *ptr;
+
+   /* argument till programmet */
+   if (argc == 2)
+   {
+      strncpy(host, argv[1], MAXSIZE);   
+   }
+   else
+   {
+      printf("Please specify a host to lookup\n");
+      return 1;
+   }
+
+   memset (&hints, 0, sizeof (hints)); /* nolla ut hints */
+   hints.ai_family = AF_UNSPEC; /* både IPv4 och IPv6 */
+   hints.ai_socktype = SOCK_STREAM;
+
+   /* hämta IP */
+   if ( getaddrinfo (host, NULL, &hints, &result) != 0 )
+   {
+      perror ("getaddrinfo");
+      return 1;
+   }
+
+   res = result;
+
+   while (res) /* loopa över alla IP-adresser */
+   {
+      switch (res->ai_family) /* IPv4 eller IPv6 */
+      {
+         case AF_INET: /* IPv4 */
+            ptr = &((struct sockaddr_in *) res->ai_addr)->sin_addr;
+            break;
+         case AF_INET6: /* IPv6 */
+            ptr = &((struct sockaddr_in6 *) res->ai_addr)->sin6_addr;
+            break;
+      }
+      /* omvandla binär-IP till läslig IP-adress */
+      inet_ntop (res->ai_family, ptr, addrstr, MAXSIZE);
+      printf ("%s\n", addrstr);
+      res = res->ai_next; /* nästa IP i listan */
+   }
+   freeaddrinfo(result); /* frigör minnet */
+   return 0;
+}